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Old 10-29-2005, 02:26 AM   #1
Rick Schu
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Default What should I log to compare a power gain between parts?

I'm going to log two different axlebacks on my car. What parameters should I log to see if there is a noticeable difference in power between the two at WOT? Or would the values be too variable run to run to compare?

I'm using the free Tari logger (latest version ECUexplorer which should have a higher resolution). I assume MAF and RPM would be the key ones, but should I log grams/sec or volts for MAF? I'm going to log on the same stretch of road, same time period (to avoid weather changes).
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Old 10-29-2005, 04:34 AM   #2
Gethin
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Dyno back to back
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Old 10-29-2005, 11:35 AM   #3
Rick Schu
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Quote:
Originally Posted by Gethin
Dyno back to back
I don't have deltadash's road dyno, if that is what you are talking about.
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Old 10-29-2005, 12:40 PM   #4
nhluhr
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Log rpm vs time, nothing else. That's the only way you can really use a logger to determine "power". Of course, you'll need to do some post-logging data analysis to convert that information to a torque/power curve.
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Old 10-29-2005, 12:43 PM   #5
drees
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Yep, MAF (either voltage or gram/s is OK), RPM, boost, timing knock correction, and TPS should do the trick.

RPM vs time as mentioned will also work, make sure you use the same stretch of road (which you will want to do regardless).
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Old 10-29-2005, 01:50 PM   #6
Rick Schu
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Quote:
Originally Posted by nhluhr
Log rpm vs time, nothing else. That's the only way you can really use a logger to determine "power". Of course, you'll need to do some post-logging data analysis to convert that information to a torque/power curve.
What's the math behind this? That is, what do these road dyno programs use to determine a hp/torque curve?
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Old 10-29-2005, 01:53 PM   #7
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Quote:
Originally Posted by Rick Schu
What's the math behind this? That is, what do these road dyno programs use to determine a hp/torque curve?
Gear ratios and total weight of car are required. If going fast enough, also need to factor in wind drag.
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Old 10-29-2005, 01:59 PM   #8
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yep, you need gear ratio*final drive, tire rolling diameter, rpm, time, mass, aero drag as a function of speed....

those should all be accomplishable in excel.
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Old 10-29-2005, 02:35 PM   #9
Jon [in CT]
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Quote:
Originally Posted by Rick Schu
What's the math behind this? That is, what do these road dyno programs use to determine a hp/torque curve?
Since all you care about is which configuration produced the most power, all you need to do is fit a line to the RPM/Time samples you log for each run.

For each configuration you should collect data from multiple runs to get a handle on your experiment's variance. You'll likely find that any difference between mufflers will be small and not statistically significant.

Last edited by Jon [in CT]; 10-29-2005 at 02:47 PM.
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Old 10-09-2007, 07:45 PM   #10
treadstone
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just log MAF grams/sec, more air flow=more power
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